Destruction of the extracellular matrix, including the collagen fibers which constitute the skeletal framework of periodontal connective tissues, is a major consequence of inflammatory periodontal disease in humans. A body of evidence suggests that this degradation of the extracellular matrix is catalyzed by a family of highly homologous proteinases that are released by endogenous and inflammatory cells. These proteinases are all believed to be zinc metalloenzymes and they are collectively referred to as matrix metalloproteinases (MMP). The five major MMP include fibroblast-type collagenase, gelatinase, and stromelysin, and neutrophil-type collagenase and gelatinase. While it is presently believed that the collective action of these MMP is responsible for the destruction of connective tissue in periodontal disease, the precise roles of the individual MMP in the actual cell-mediated process is not yet well understood. Such knowledge can only be obtained from the study of the degradation of matrix macromolecules by live cells in which the entire catabolic machinery is intact. The involvement of specific MMP must, therefore, be assessed through their specific inhibition. In this study specific potent inhibitors of each of the five MMP will be prepared and their efficacy in blocking the breakdown of matrix macromolecules (types I, IV and V collagens and gelatins, fibronectin, laminin, proteoglycan core protein) by live fibroblasts and neutrophils will be assessed. These experiments should allow us to establish the role of each MMP in the cell- mediated destruction of each physiological substrate. The design of the inhibitors will be based on extensive studies of the peptide substrate specificity of each of the five MMP. The inhibitors will be substrate analogs in which the scissile peptide bond is replaced with a functional group (phosphinate, sulfide, sulfoxide, sulfone, ketone and fluoroketone) capable of interacting with the active site zinc atom of each MMP. This principle has been used previously to develop inhibitors of angiotensin converting enzyme which are now being widely used to control hypertension in humans. Our data indicate that, although highly homologous, the five MMP have sufficiently different peptide substrate specificities to permit construction of potent inhibitors which are highly specific for each of the five enzymes.